The present invention relates to a paper delivery apparatus of a printing machine, and more particularly, to a paper delivery apparatus for holding printed sheets being discharged from the printing machine one by one at regular intervals in a vertical direction, carrying the sheets downward for a preset distance to a specific position every time each printed sheet is ejected from the printing machine, and successively dropping it to stack on a receiving tray.
As printed sheets are stacked in succession immediately after printing, there occurs the so-called "setoff" wherein the back side of the following printed sheet will be smudged with ink when laid on the preceding printed sheet. This tendency is remarkable in the case of printing on nonabsorbent papers such as postcards and the like.
The present applicant, therefore, invented an apparatus as shown in FIG. 13. In this drawing, a printed sheet W is discharged from the printing machine along a direction perpendicular to the paper surface illustrated, entering through an entrance route E. Near the entrance route E is provided a holding means 300 for receiving and holding the printed sheets W one by one.
The holding means 300 has at least a pair of belt mechanisms disposed in the vicinity of both side edges of the printed sheet W. Each belt mechanism comprises upper and lower pulleys 301 and 302 and a belt 303 wound around these pulleys. On the belts 303 are provided paper receiving sections 304 for holding both side edges of the printed sheet W, at an equal space in the direction of movement of the belt 303.
In the drawing, the printed sheet W being discharged from the printing machine is supported by the paper receiving sections at the uppermost stage which are ready for receiving the printed sheet W. Every time the printed sheet is ejected from the printing machine, the belt mechanisms of the holding means 300 is driven to move the printed sheet on the paper receiving sections 304 successively downward until the next paper receiving sections 304 come to the uppermost stage receive the following printed sheet. With the rotation of the holding means 300, the paper receiving sections 304 move downward as low as a specific position, and then the printed sheet W supported on the paper receiving sections 304 goes down off the paper receiving sections 304, to be received in a receiving tray 305 located below.
While the printed sheet W is held by the holding means 300, the ink on the paper dries and accordingly no setoff will occur on the printed sheet W stacked in the receiving tray 305.
If the printed sheet W in the receiving tray 305 moves, the printed surface of the printed sheet is rubbed to be smeared. Therefore, the width of the tray 305 has been set to agree with the width of the printed sheet W as much as possible. In the meantime, according to the delivery apparatus previously stated, the spacing between the pair of belts 303, 303 has been set larger than the width of the printed sheet W with the facility of receiving the printed sheet W.
Therefore, there is a positional difference, in the direction of width, of the printed sheet W held by the paper receiving sections 304 of the belts 303. If, therefore, the printed sheet W dropping from the holding means 300 is off the proper position, the side edge of the printed sheet W will touch the upper end of the side wall of the receiving tray 305 as shown in FIG. 13, resulting in improperly stacked printed sheet W in the tray 305.